1. Field of the Invention
The present disclosure generally relates to overload protection mechanisms adapted for use with an active material actuator, and in particular, to a regulation/overload protection mechanism that utilizes piezoelectric or piezoresistive effect to autonomously regulate and/or interrupt an activation signal.
2. Discussion of Prior Art
In the Martensitic phase, shape memory alloy (SMA) actuators are activated by exposing the SMA component to a thermal activation signal. The signal causes the component to transform to the Austenitic phase, which presents a higher modulus and contracted length. As shown in prior art FIG. 1, transformation is typically used to do work, where the component 1 is coupled to and the change in length maneuvers a load 2. When the component 1 is activated, but the load 2 is unable to be maneuvered (e.g., due to external conditions, damaged parts, etc.), an overloading event that may overheat or otherwise damage the component 1 may occur.
To protect against overloading, conventional SMA actuators typically use mechanical spring mechanisms 3 (FIG. 1), sometimes in combination with a micro-switch or photointerruptor, to alleviate excess strain in the SMA component 1 during such an event. These mechanisms 3, however, present various concerns in the art, including, for example, increased overall actuator size, reduced packaging within the actuator, and increased weight. Accordingly, there is a need in the art for a more compact mechanism and/or method of providing overload protection to SMA actuators.